Dietary changes since the early 1960s have fuelled a sharp increase in the amount of mined phosphorus used to produce the food consumed by the average person over the course of a year, according to a new study led by researchers at McGill University, Montreal.

Between 1961 and 2007, rising meat consumption and total calorie intake underpinned a 38 percent increase in the world's per capita "phosphorus footprint," the researchers conclude in a paper published online in Environmental Research Letters.

The findings underscore a significant challenge to efforts to sustainably manage the supply of mined phosphorus, a non-renewable resource widely used in fertilisers. When phosphorus is lost through agricultural runoff or sewage systems, it can cause serious water pollution. In addition, because deposits are heavily concentrated in a few countries, global supplies and prices for the resource are vulnerable to geopolitical tensions.

In recent years, many researchers have explored how human activity has altered the phosphorus cycle in the environment and how management of phosphorus could be altered to ensure long-term sustainability. The McGill researchers said their study sheds more light, in particular, on how dietary choices have affected the intensity of phosphorus use around the world.

Geneviève Metson, the study's lead author said on Thursday (17th January), "Our results demonstrate that changes in diet can be a significant part of the strategy for enhancing sustainability of phosphorus management. In particular, reduced consumption of meat, and especially beef, in countries with large phosphorus footprints could put a big dent in demand for mined phosphorus – since it takes many kilograms of feed, which is fertilized, to produce a kilogram of meat."

The McGill researchers' findings come no more than a week after a study by the Institution of Mechanical Engineers called for vast systemic changes to food production and consumption patterns to curb waste. IME researchers said food waste is somewhere in the region of 50 percent worldwide, and warned that production of resource-dense foods is increasing strain on finite resources. The researchers pointed out that it takes 20 to 50 times more water to produce one kilogram of meat than one kilogram of vegetables; they made particular mention of beef production. 

Metson and her co-authors, Professor Elena M. Bennett, also at McGill, and Professor James J. Elser of Arizona State University, computed phosphorus-footprint values based on annual country-by-country diet data from the UN Food and Agriculture Organization. They calculated the total amount of phosphorus applied to food crops for humans and animals by using fertiliser-application rates available through the International Fertiliser Association, among other sources. The authors also examined the statistical relationship between economic development and phosphorus-footprint values, and developed scenarios to consider the relative importance of diet changes.

Professor Bennett said, "It is really remarkable how much influence changes in diet have had on our demand for this very limited resource. As research in this area proceeds, it would also be interesting to learn how much of the phosphorus used in food production is able to be recycled and how much is currently reused. Food waste and human waste generally aren't reused today, but can be a valuable resource if turned into fertiliser or compost for use on nearby agricultural fields."